1. Field of the Invention
The present invention relates to a fan and the rotor structure thereof.
2. Description of the Prior Art
Generally, in a conventional fan, the shaft and the case of the rotor structure are engaged by interference fit. In a large fan with significant size and weight, however, the shaft and the case may separate in operation due to the weight of the rotor structure. Typically, a rivet joint is used for large fans to engage the shaft and the case. With a rivet joint, the contact area of the shaft and the case increases to support the increased weight of the rotor structure.
FIG. 1 illustrates a rotor structure 100 in a conventional large-scale fan. The rotor structure 100 has a case 102, a fan blade 104, a copper sheath 106, and a shaft 108. The shaft 108 is disposed in the copper sheath 106 by interference fit, and the copper sheath 106 is riveted to the case 102 by the rivet joint 110. Further, an electrocoating layer is coated on the case 102.
In the conventional rotor structure 100, however, the copper sheath 106 is riveted to the case 102 by compression, so that the shock resistance of the rotor structure is limited. When the weight of the rotor structure increases, it is possible that the rivet joint 110 will fracture or separate due to the weight thereof, and the shaft 108 and the case 102 may separate.
Further, the copper sheath 106 is riveted to the case 102 by compression, so a portion of the electrocoating layer on the case 102 is scraped by the copper sheath 106. Thus, due to degradation of the electrocoating layer, the case 102 and the copper sheath 106 are exposed and may rust. In addition, a gap exists between the case 102 and the copper sheath 106 due to the rivet joint 110. Further, the shaft 108 is disposed in the copper sheath 106 by interference fit, such that a portion of the shaft 108 is exposed and may rust. In either case, the rotor structure and other elements in the fan may be damaged.